Toward a Reliable Chipless RFID Humidity Sensor Tag Based on Silicon Nanowires

This paper presents a chipless radio frequency identification (RFID) sensor tag having both identification and sensing capabilities. It is based on one resonant scatterer operating as a signal processing antenna in the 3-7.5 GHz band. The scatterer is used to monitor a physical parameter variation, as well as to identify the remote sensor. To make a resonator sensitive to the humidity, silicon nanowires are deposited on the tag surface using a simple process. The tag needs only one conductive layer so that it can be directly printed on the product to sense and to identify. Measurements done using a bistatic radar configuration in the frequency domain validate this concept. To demonstrate the reliability of such an application, two chipless RFID sensors placed in various environments are simultaneously detected using an anticollision technique based on spectral separation.